How to Use INCR Command in Redis: Simple Guide

Use the INCR command in Redis to increase the integer value stored at a key by one. If the key does not exist, INCR sets it to 1. This command only works on keys holding integer values stored as strings.

Syntax

The INCR command syntax is simple and takes one argument:

• key: The name of the key whose integer value you want to increment.

If the key does not exist, Redis creates it with the value 1. If the key contains a value that is not an integer, Redis returns an error.

redis

INCR key

Example

This example shows how to increment a counter stored in Redis using the INCR command. It demonstrates incrementing an existing key and creating a new key if it does not exist.

redis

127.0.0.1:6379> SET page_views 10
OK
127.0.0.1:6379> INCR page_views
(integer) 11
127.0.0.1:6379> INCR new_counter
(integer) 1

Output

(integer) 11
(integer) 1

Common Pitfalls

Common mistakes when using INCR include:

• Trying to increment a key holding a non-integer value, which causes an error.
• Assuming INCR works on keys with string values that are not integers.
• Not handling the case where the key does not exist (though Redis sets it to 1 automatically).

Example of wrong and right usage:

redis

127.0.0.1:6379> SET name "Alice"
OK
127.0.0.1:6379> INCR name
(error) ERR value is not an integer or out of range

# Correct usage:
127.0.0.1:6379> SET visits 5
OK
127.0.0.1:6379> INCR visits
(integer) 6

Output

(error) ERR value is not an integer or out of range
(integer) 6

Quick Reference

Command	Description
INCR key	Increment the integer value of key by one
INCRBY key increment	Increment the integer value of key by a specified amount
SET key value	Set the string value of a key
GET key	Get the value of a key

Key Takeaways

Use INCR to increase an integer stored at a key by one in Redis.

INCR creates the key with value 1 if it does not exist.

INCR only works on keys holding integer values stored as strings.

Trying to INCR a non-integer value causes an error.

Use INCRBY to increment by values other than one.